Virtual training environments are appropriate to train complex tasks that require collaboration and interaction among the members of a team, especially if training in reality is not possible, too expensive or too dangerous. The field study reported in this paper compared three training conditions (virtual condition, standard condition, and control condition). The participants were police officers who were being trained in the communication between ground forces and a helicopter crew during an operation. This task (like many other tasks of the police, fire brigade and emergency services) is of high complexity and has no single "correct" solution, is based on specialization of tasks within a team, requires intensive communication among team members, and consists of situations in which human beings are in danger. Learning outcomes and knowledge transfer were measured as dependent variables. The results validate that virtual training was as efficient as standard training with regard to knowledge acquisition, and it was even more efficient with regard to knowledge transfer. With regard to the perceived value of the training, the participants judged standard training to be better than virtual training (except for training satisfaction, where no difference was found between standard and virtual training). These results indicate that virtual training is an effective tool for training in complex tasks that require collaboration and cannot fully be trained for in reality.